1. Technical Field
The present invention relates generally to sash window assemblies, and particularly to such a sash window assembly having a latch device incorporated in a vertically slidable, inwardly tiltable sash.
2. Related Art
Vertically-sliding windows having vertically openable/closable, inwardly-tiltable sashes are known that are mounted in openings of exterior walls of housings, for example. For such windows, there have been proposed latch devices that fasten an upper portion of the sash to a vertical frame member of a window frame with respect to the depth direction and vertically guide the sash, and that support the sash such that it can be operated so as to tilt inward when the fastening is released. (See, for example, JP-A-2003-49573, U.S. Pat. No. 5,139,291, and U.S. Pat. No. 6,183,024.)
The latch devices disclosed in the above-mentioned references are made up of a case, an engaging member that is accommodated in the case and that projects toward the vertical frame member, a spring that urges the engaging member in the projecting direction, and an operating member that is operated for retracting the engaging member into the case against the urging force of the spring. The latch devices are mounted respectively to intersecting portions where an upper frame element (a mating frame element) of the sash and the two vertical frame elements thereof intersect, the intersecting portions being located at both left and right ends in the upper portion of the sash. An indentation is formed in each intersecting portion where one of the lateral end portions of the upper frame element and the upper end portion of one of the vertical frame elements intersect, and each latch device is fixed to the sash by inserting the case into the indentation and then fastening the case with screws etc. More specifically, as shown in FIG. 2 of U.S. Pat. No. 5,139,291 and FIG. 14 of U.S. Pat. No. 6,183,024, the indentation is formed in the intersecting portion of the upper frame element and the vertical frame element in such a manner that the indentation is opened contiguously across the top surface of the upper frame element and the depth-direction surface of the vertical frame element, and the latch device is mounted by being slid along the indentation in the lateral direction from the side of the vertical frame element.
However, with the conventional latch devices such as those disclosed in the above-mentioned references, it is necessary to form a large indentation extending across the intersecting portion of the upper frame element and the vertical frame element for inserting the case, and this gives rise to a problem that the strength of the sash is reduced or that it becomes necessary to provide reinforcement measures for preventing this strength reduction. More specifically, it is the engaging member of the latch device that restricts the upper end portion of the sash from moving toward the indoor side, and thus, when force such as outdoor wind pressure is applied to the sash from the out-of-plane direction, the force is transmitted from the upper frame element and the vertical frame element to the vertical frame member through the case and the engaging member. At that time, the case may break open the indentation at the intersecting portion between the upper frame element and the vertical frame element, and the indentation may deform so as to open up. Such deformation reduces the strength in the periphery of the indentation, and this strength reduction negatively affects the performance (strength, hermeticity, watertightness, etc.) of the sash window assembly.